The present invention relates to an electrophotographic apparatus.
An electrophotographic process for obtaining a plurality of duplicated copies by repeating the development step and the transfer step based on an electrostatic latent image formed on a photosensitive conductor such as selenium, has been well known from U.S. Pat. No. 2,951,443.
Another electrophotographic process for obtaining a plurality of duplicated copies by utilizing persistent conductivity due to fatigue caused by light image projected on the photosensitive conductor, has also been disclosed in for example Japanese Patent Application Publication Nos. 20,347/65 and 42,469/71. As a process similar to a process for utilizing persistent conductivity of such photosensitive conductor, an electrophotographic process for obtaining a plurality of duplicated copies by utilizing a conductive latent image formed by metallic silver formed on the exposed portion of silver salt photographic emulsion has been well known. Moreover, an electrophotographic process for obtaining a plurality of duplicated copies by repeating uniform charging, uniform exposure and transfer steps based on toner image permanently or temporarily formed on a photosensitive conductor has been well known from, for example, Japanese Patent Application Publication No. 21,095/65 and Japanese Patent Laid-open No. 8,730/72. A further electrophotographic process for obtaining a plurality of duplicated copies by repeating the formation of an electrostatic latent image formed on a charge retentive member having a dielectric layer by modulating a corona ion flow based on the electrostatic latent image formed on a photoconductive screen having, for example, a plurality of fine apertures, has been well known.
While as means for fixing toner image formed on a recording paper in the prior electrophotographic technique the feature of fixing toner image by the light emitted from an incandescent lamp such as halogen lamp or xenon electronic-flash lamp, has been disclosed in, for example, U.S. Pat. No. 2,807,703, it is very preferable to utilize the incandescent lamp or the flash lamp for fixing the toner image since the time upto starting of fixation is very short and particularly in the case of using the flash lamp the toner image can be fixed almost without heating the record paper so that the fixing device can not be heated and thus a fear or causing a fire does not occur. However, when the electrophotographic apparatus is constituted by applying such a fixing device having emitting means to the above electrophotographic apparatus for obtaining a plurality of duplicated copies by only one exposure, the electrostatic latent image formed on the photosensitive conductor or the photoconductive screen disappears by the light leaked from the fixing device during the multiple copying step or in the electrophotographic apparatus for obtaining a plurality of duplicated copies based on a master toner image formed on the photosensitive conductor uneven density occurred by a partial projection due to the leakage light from the fixing device or in an electrophotographic apparatus utilizing the persistent conductivity of the photosensitive conductor a disappearance of image occurred by increase of whole or a partial conductive latent image due to the leakage light. In order to eliminate these disadvantages it is provided that the fixing device is constructed so that the light should not be leaked. It is, however, found that realization of such a construction is very difficult since the recording paper with toner image thereon must be passed through the fixing device. Even if the conveying path for recording paper is bent to prevent the light from leaking, its construction becomes complicated and expensive. Particularly, when the light for fixing with a value in extent capable of selectively fixing only the toner image is generated by a large light source of simultaneous emitting type such as a xenon electronic-flash lamp, it is very difficult to keep the leakage light inside to an extent that the leakage light does not affect the photosensitive charge retentive member.